CnAlias - Random CNAME Aliases

CnAlias - Random CNAME Aliases

This module is designed to return one or more random aliases using CNAME (Canonical Name) records.

It specifically generates a random CNAME alias record in the format cnalias######.yourdomain.com, where ###### represents a random number.

The idea is that if the client/resolver decides to resolve this further, it will result in the generation of yet another alias, theoretically leading to a resolution of infinite chain of random aliases. In practice, however, most modern resolvers will terminate the resolution after encountering several consecutive alias records.

Note that this feature provides the same functionality as requesting the CNAME record for the generic alias feature. Responding with multiple records (aliases) in a single response is also supported.

⚠BEWARE⚠This can potentially lead to amplification effect (DoS) or domain lock-up (DoS).

Category: Aliases

Tags: Amplification, Domain Lock-Up, Denial of Service

RFCs: RFC1034

Format 

cnalias.<NUMBER>.yourdomain.com

Where:

  • The <NUMBER> parameter defines how many aliases should be generated in the response.

Examples

By default, it returns a single CNAME alias:

# dig cnalias.yourdomain.com @127.0.0.1

; <<>> DiG 9.18.10-2-Debian <<>> cnalias.yourdomain.com @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 35958
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;cnalias.yourdomain.com.		IN	A

;; ANSWER SECTION:
cnalias.yourdomain.com.	60	IN	CNAME	cnalias855038.yourdomain.com.

;; Query time: 4 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Wed Oct 16 09:36:57 +04 2024
;; MSG SIZE  rcvd: 82

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Same example as above, but this time we explicitly specify that we want to receive a single CNAME record:

# dig cnalias.1.yourdomain.com @127.0.0.1

; <<>> DiG 9.18.10-2-Debian <<>> cnalias.1.yourdomain.com @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 23974
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;cnalias.1.yourdomain.com.	IN	A

;; ANSWER SECTION:
cnalias.1.yourdomain.com. 60	IN	CNAME	cnalias684642.1.yourdomain.com.

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Wed Oct 16 09:36:59 +04 2024
;; MSG SIZE  rcvd: 86

Download PCAP File


In this case, we specify that we want to receive five CNAME aliases:

# dig cnalias.5.yourdomain.com @127.0.0.1

; <<>> DiG 9.18.10-2-Debian <<>> cnalias.5.yourdomain.com @127.0.0.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 35342
;; flags: qr aa; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;cnalias.5.yourdomain.com.	IN	A

;; ANSWER SECTION:
cnalias.5.yourdomain.com. 60	IN	CNAME	cnalias217971.5.yourdomain.com.
cnalias.5.yourdomain.com. 60	IN	CNAME	cnalias62435.5.yourdomain.com.
cnalias.5.yourdomain.com. 60	IN	CNAME	cnalias615162.5.yourdomain.com.
cnalias.5.yourdomain.com. 60	IN	CNAME	cnalias737434.5.yourdomain.com.
cnalias.5.yourdomain.com. 60	IN	CNAME	cnalias25705.5.yourdomain.com.

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Wed Oct 16 09:37:00 +04 2024
;; MSG SIZE  rcvd: 260

Download PCAP File


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